Thermally responsive valve devices are employed as the principal temperature control means in engine cooling systems. It is well known in the art that existing thermostatic valve devices during initial opening operation permit the temperature of the system controlled to fluctuate. Such fluctuations are undesirable. In an attempt to solve this problem, some thermally responsive valve devices have included means for regulating fluid flow at low fluid rates. U.S. Pat. Nos. 2,926,853 and 3,182,911 disclose thermally responsive valve devices which have multiple closure members. However, such multiple closure members, even though providing fluid control, do not provide good metering or fine regulation of fluid flow, required for temperature control stability under dynamic operating conditions.
It is an object of this invention to provide a thermally responsive fluid valve device which has such excellent regulation of fluid flow.
Other objects and advantages of this invention reside in the construction of parts, the combination thereof, the method of manufacture, and the mode of operation, as will become more apparent from the following description.